The present invention relates to a steering angle warning system, an aircraft and/or tow vehicle including a steering angle warning system, and a method of warning against excessive steering angle on an aircraft.
Movement of an aircraft on the ground is often effected by a towing tractor engaged with the aircraft nose landing gear. It may be possible for the towing tractor to turn the nose landing gear through an excessive steering angle and damage the nose landing gear assembly.
Some systems are known to provide a warning against excessive steering angle. For example, it is known to have coloured markings on the rotatable leg of the nose landing gear and coloured markings on the body of the aircraft and/or on a stationary part of the nose landing gear. The markings are so arranged that their alignment with one another acts as a visual warning that the nose landing gear has turned through an excessive angle. Such a system may, however, be ineffective as it can be adversely affected by factors such as poor visibility and driver distraction.
Another warning system is described in U.S. patent application Ser. No. 10/795,539 (US 2005/0196256). The warning system includes two ultrasonic sensors mounted on a towing tractor, at least one of the sensors being arranged to detect the presence of the aircraft structure above it when the steering angle is relatively low, and to fail to detect the aircraft structure when the steering angle is relatively large. Thus when one of the sensors fails to detect the presence of the aircraft structure, the system alerts the operator that the steering angle may be becoming too large. Such a system requires the use of a specifically designed tractor and is thought to be unduly complex. The system also relies on detecting a signal reflected from the aircraft structure and may therefore be adversely affected by dirt or foreign objects on the detector. Furthermore, the system needs to be calibrated in dependence on the particular aircraft model being towed.